Biology Reference
In-Depth Information
of bacterial RhoGEFs EspT and EspM which override the cellular Rho GTPase
signaling ( Wong et al., 2012a,b ).
Apart from secreting effector proteins that cause apoptosis, EPEC also
secretes effectors that are anti-apoptotic (see subversion by the T3SS). The bal-
ance between these processes remains a relatively unexplored subject.
CLINICAL MANIFESTATIONS
Transmission
EPEC strains are transmitted via the fecal-oral route through direct contact, via
contaminated food and water sources, or fomites acting as vehicles. Hospitals
may also serve as a source of infection ( Blake et al., 1993 ). In addition, one
case study described the concurrent infection of a child and pet dog with the
same human EPEC clone, indicating the possibility of household pets acting as
reservoirs ( Rodrigues et al., 2004 ). Outbreaks in nurseries and daycare are no
longer common, but in those cases where disease had occurred, the source of
infection was rarely identified. However, two outbreaks in Chongqing, China,
affecting a total of 69 neonates, were sourced back to one mother, and were
determined to have spread via medical staff's hands ( Wu and Peng, 1992 ). In
2000, 45 Japanese students (ages 12-15 years) became infected with aEPEC
whilst on a fieldwork program held at a farm. A contaminated water source
was determined to be the vehicle for transmission, with a marked difference
between rates of attack for those students who had drank the tap water (86.1%)
and those who had washed their hands with the water (26.3%). This outbreak is
an example in which EPEC may have been transmitted from animals via a water
source to humans, as the provided water was from a brook which also served
as a water source for farm animals ( Yatsuyanagi et al., 2003 ). Conversely, an
outbreak of diarrheal illness affecting >100 people in the US was linked to a sin-
gle buffet serving uncooked and cooked food. Environmental health inspectors
had observed extensive contact between uncooked seafood and eggs, and fresh
fruits and vegetables ( Hedberg et al., 1997 ). Person-to-person transmission was
highlighted by a Finnish school aEPEC outbreak, where spread to associated
households was observed in one third of those who had responded to the survey
questionnaire ( Viljanen et al., 1990 ).
Clinical features
EPEC infections often last between 5-15 days, but prolonged illness can occur
( Lacroix et al., 1984 ; Hill et al., 1991 ). Diarrhea is the most common clinical
presentation of EPEC, with recent studies suggesting an association between
atypical strains and persistent diarrhea ( Levine et al., 1978 ; Afset et al., 2004 ;
Nguyen et al., 2006 ). Diarrhea may contain mucus but rarely blood. Greater
than 90% of patients present with diarrhea, with additional features observed
Search WWH ::




Custom Search